CD8A and neoplasm: The fraction of CD8+ cytotoxic T lymphocytes (CTLs) was significantly lower in superficial tumor and in the invasive margin than in adjacent normal mucosa (P = 3 × 10−5 and P = 3 × 10−3, respectively; Fig. 3a) and CTLs were more distant from epithelial cells in tumor-containing regions than in normal mucosa (P < 10−16); Fig. 3b,c).